image calling a javascript function

[sourav]

PASSWORD PROTECTION GATEKEEPER

Theres one HTML page having a J'script that creates new users and passwords.

On the secong page you need to login with that username and password. On submission u are taken to a new page of 8 characters name.

I want to replace the default form submit button with an image. The button calls a function check() . The javascript part of the code is given below.

The invalid entry prompts are OK. But the new page is not opening.

<SCRIPT LANGUAGE="JavaScript">
<!-- Begin
var params=new Array(4);
var alpha="ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHI";
function check(form) {
which=form.memlist.selectedIndex;
choice = form.memlist.options[which].value+"|";
if (choice=="x|") {
alert("Please Select Your Name From The List");
return;
}
p=0;
for (i=0;i<3;i++) {
a=choice.indexOf("|",p);
params[i]=choice.substring(a,p);
p=a+1;
}
h1=makehash(form.pass.value,3);
h2=makehash(form.pass.value,10)+" ";
if (h1!=params[1]) {
alert("Incorrect Password!"); return; };
var page="";
for (var i=0;i<8;i++) {
letter=params[2].substring(i,i+1)
ul=letter.toUpperCase();
a=alpha.indexOf(ul,0);
a-=(h2.substring(i,i+1)*1);
if (a<0) a+=26;
page+=alpha.substring(a,a+1); };
top.location=page.toLowerCase()+".html";
}
function makehash(pw,mult) {
pass=pw.toUpperCase();
hash=0;
for (i=0;i<8;i++) {
letter=pass.substring(i,i+1);
c=alpha.indexOf(letter,0)+1;
hash=hash*mult+c;
}
return(hash);
}
// End -->
</script>